镁的引入对微生物加固砂土试验的影响

The Effect of Magnesium on the Experiment of Microbial Reinforcement of Sand

微生物沉积碳酸盐(microbially induced carbonate precipitation,MICP)技术是土木工程领域中一种新型的地基处理技术,其主要通过微生物诱导产生的碳酸盐沉淀胶结砂土颗粒,从而提高其力学性能。目前,MICP加固过程中Ca 2+作为生成CaCO 3沉淀的主要来源,但是对其他金属离子和矿化产物以及矿化产物之间结合作用的相关研究较少。选取6种不同的Mg 2+/Ca 2+物质的量比工况,通过碳酸盐沉淀试验和无侧限抗压强度试验,分析MICP技术处理砂土影响的效果。利用扫描电子显微镜和X射线衍射仪,初步探讨了微生物固化砂土的机理。结果表明:随着Mg 2+/Ca 2+物质量比的增加,固化后砂样的碳酸盐含量降低;较低Mg 2+/Ca 2+物质的量比提高了其无侧限抗压强度;在Mg 2+/Ca 2+=0.1/0.4时,砂样的强度获得最大值;但较高Mg 2+/Ca 2+物质的量比抑制了碳酸盐的析出,降低了其强度;随着Mg 2+/Ca 2+物质的量比的增大,矿物成分含有方解石、球霰石和镁方解石等各种混合物,矿物成分发生了变化。

Microbially induced carbonate precipitation(MICP)is a new technology of foundation treatment in the field of civil engineering which improves the mechanical properties mainly through carbonate precipitation and cementation of sand particles induced by microorganisms.At present,Ca 2+is the main source of CaCO 3 precipitation in the process of MICP reinforcement,but there are few studies on the interaction between other metal ions and mineralized products.Six different conditions of Mg 2+/Ca 2+molar ratio were selected,the effect of MICP on sand solidification was analyzed by carbonate precipitation test and unconfined compressive strength test.The mechanism of microbial solidification of sand was preliminarily discussed by scanning electron microscope and X-ray diffractometer.Results show that with the increase of Mg 2+/Ca 2+molar ratio,the content of carbonate in solidified sand decreases;the low molar ratio of Mg 2+/Ca 2+increases the unconfined compressive strength;and the strength reaches the maximum value when Mg 2+/Ca 2+=0.1/0.4;but with the increase of Mg 2+/Ca 2+molar ratio,the precipitation of carbonate is inhibited and the strength is reduced.With the increase of Mg 2+/Ca 2+molar ratio the mineral composition changes with various mixtures such as calcite,globular aragonite and magnesium calcite.